How do I use Proxies when compositing strips?
In the original approach, Offset and Crop were applied to the strip.  This approach did not work.
However, it does work when Offset and Crop are applied to a transform.  Click on the strip, then in the menu, choose Add -&gt; Effect Strip -&gt; Transform.   This then creates a green transform block for the strip (in the next channel).  By applying the Offset and Crop to the transform and then regenerate the proxies, everything worked as expected.